The visuals, the concept, the song and the message.
It's not a revolutionary concept, that's fine. But abusive relationships and compulsive obsession is definitely not a concept in K-Pop songs, and not explicitly like this. So the way the music producers were able to put EJAE's version which was about one side of the relationship into both being OBSESSED with each other was top tier (At least for me).
The concept images reminded me a lot of F(X)'s one, and both of them pulled off well. Nothing wow, but the creepy vibe it had on Psycho's concept photos is to die for. They all look amazing.
I dislike SM'E for only bringing Red Velvet when the building is on fire, but they don't disappoint me either with songs or concept… At least for girl groups.